A heuristic strategy for converting Ni-rich hydroxide precursors into sustainable fast-charging cathodes for next-generation lithium-ion batteries

Ni-rich R-3m polycrystalline layered oxides (LiNi_1-xM_xO_2; M = Mn, Co, Ti; 0 ≤ x ≤ 0.2) are among the most promising Li-ion battery cathodes, combining high energy density with cost-effective production. However, their fast-charging capability is hampered at high voltages due to sluggish Li⁺ transport and structural degradation. Herein, we report a heuristic, solid-state co-doping strategy employing boron (B³⁺) and titanium (Ti⁴⁺) to simultaneously engineer the bulk structure and surface chemistry of Ni-rich cathodes. The co-doped materials demonstrate exceptional stability in lithium-graphite full cells, retaining >86% capacity after 500 cycles at a 4C charge rate, even across elevated cutoff voltages (4.3-4.5 V) and high Ni contents (80–100 mol%). Multiscale characterization reveals three critical morphological features: (i) radially arranged nanosheet-like grains that alleviate anisotropic lattice strain; (ii) an in-situ formed Li-B-O surface layer that mitigates electrolyte decomposition at high voltage; and (iii) a defect-mediated cation-mixed interphase that pillars the layered structure under extreme delithiation. Extension of this strategy to ultra-high Ni systems, including LiNi_0.9Co_0.1O₂ and LiNiO₂, yielded comparable enhancements. Mechanistic insights further enabled the rational selection of earth-abundant pillaring elements, enhancing the scalability and sustainability of the proposed doping system. This work underscores the potential of defect phase engineering and microstructural control without reliance on group V/VI dopants for the development of robust, fast-charging Ni-rich cathodes.